Dispensing devices such as those described in Wright, U.S. Pat. No. 3,709,437, issued Jan. 9, 1973 ("Wright 437"), and Wright, U.S. Pat. No. 3,937,364, issued Feb. 10, 1976 ("Wright 364") are known for mixing a foamable liquid held in a reservoir with air to form a foam which can be dispensed from the device. In the Wright 437 device, for instance, mixing of the air and the foamable liquid occurs as the result of the compression of a deformable reservoir of the foamable liquid, or as shown in FIG. 8, by the action of a deformable air bag which when compressed both forces foamable liquid out of the reservoir and forces air to mix with the foamable liquid. Similarly, a deformable reservoir foam dispensing device which is operable in any position is shown in Wright 364. These devices work well, but it is believed that foam dispensing devices specifically designed for reservoirs which are not deformable would be advantageous in some instances.